Cranes and derricks installed on floating surfaces must have a what?

The answer

Under OSHA's construction crane standard, cranes and derricks installed on floating surfaces (such as barges or pontoons) must have a boom angle or radius indicator that is readily visible to the operator. This requirement comes from 29 CFR 1926.1437, the section covering floating cranes/derricks and land cranes/derricks mounted on barges.

A boom angle or radius indicator tells the operator how steeply the boom is raised and, in turn, the crane's load radius. On a floating platform this information is critical, because both the load and the motion of the water affect how much capacity the crane safely has at any given moment.

Why floating cranes need extra safeguards

A crane on solid ground sits on a stable, level base. A crane on the water does not. Waves, wakes, tides, and the shifting of the load all cause the vessel to list (tilt side to side) and trim (tilt front to back). That constant movement changes the crane's effective load radius and can rapidly erode stability. To manage this, 1926.1437 requires additional equipment and information that a land crane may not need, including:

• A boom angle or radius indicator readily visible to the operator (the answer here).
• List and trim indicators near the operator so they can monitor the vessel's tilt.
• Adjusted, often reduced, load charts that account for the floating condition and dynamic forces.
• Attention to the vessel's own stability and buoyancy so the combined crane-and-barge system stays within safe limits.

List and trim describe the two ways the platform can tip: list is the sideways angle, trim is the fore-and-aft angle. Monitoring both lets the operator stop before the platform becomes unstable.

Why other answers are wrong

Distractors on this question often name safety devices that apply to all cranes, not the specific floating requirement:

• "An anti-two-block device" or "a boom hoist limiter" are general crane safety devices, not the distinguishing floating-surface requirement being asked about.
• "A fire extinguisher" or "outriggers" miss the point; outriggers stabilize land cranes, and a floating crane relies on vessel stability, not outriggers.
• Answers that omit "readily visible to the operator" are incomplete, because the standard emphasizes that the indicator must be positioned where the operator can actually see it while working.

The bigger picture

The theme of 1926.1437 is that putting a crane on the water introduces motion and stability hazards that do not exist on land, so operators need real-time feedback about boom position and vessel attitude. The boom angle/radius indicator, combined with list and trim indicators and de-rated load charts, gives the operator the information to keep the lift within the crane's and the vessel's safe capacity as conditions change.